PL189132B1 - Mold block with air flow control - Google Patents

Abstract

A mold block which is used in a moving mold tunnel comprises first and second mold block sections (3, 5) which meet at their parting faces (4, 6) to close the mold block. Each mold block section has a product shaping interior surface (15, 35) and an air movement passage (11, 30). An air flow controller is provided in each mold block section (3, 5). Through various different positionings of the two air flow controllers, the mold block can be operated in any one of four different modes including a first vacuum forming mode in which air is withdrawn from the mold block through both of the mold block sections (3, 5), a second vacuum forming mode in which air is withdrawn from the mold block through only one of the mold block sections, a third cooling mode in which air is introduced into the mold block through one of the mold block sections and is then withdrawn from the other of the mold block sections and a fourth blow molding mode in which pressure within the mold block is released through both mold block sections (3, 5).

Description

The present invention relates to an air-flow controlled mold body which is used in a moving mold tunnel and is particularly useful in forming a profiled plastic pipe.

Corma Inc. of Toronto, Ontario, Canada, has a long history of manufacturing and marketing plastic pipe forming equipment as set forth in US Patent 5,002,478, issued March 26, 1991 (Loupe). The equipment includes sections of the mold body that travel on an endless path and meet each other to form complete mold bodies that are transported along a moving mold tunnel. Corma mold bodies have slotted openings on the inside surfaces of the mold bodies that are used to suck in air from the outside of the mold bodies. Such vacuum gap mold bodies have proved to be extremely effective in vacuum forming a plastic tube, where a vacuum is generated in both sections of the mold body. They are also used to a lesser extent in the blow molding of tubes.

Currently, a Corma mold body is not used for cooling where it is very important to provide cooling for both the pipe and the mold bodies used in making the pipe. Such cooling greatly increases the productivity of the mold for the production of the pipe.

US 4,718,844 (Dickhut) discloses a mold body having cooling channels that extend between the molding surface and the outer surface of the mold body. These channels do not supply cooling air directly to the forming area, nor do they include controls for air movement in the channels and between the mold body sections.

According to the invention, a controlled air flow mold body for use in a moving mold tunnel comprising first and second sections each having an interior article-forming surface and a parting surface is characterized in that each mold body section further comprises a first air flow channel. each channel has an inlet and a first opening in each channel for the inner product-shaping surface and a second opening for the parting surface, the second channel opening in the first section of the mold body communicating with the second channel opening in the second section of the mold body when the mold body sections are are closed at their partition surfaces, and have first and second air flow valves, each of the valves being independently controlled between an air flow position and an air block position, furthermore the first air flow valve is located between the first opening and an inlet in the duct first the mold body section, and a second air flow valve is positioned between the second opening and the first opening in the passage of the second mold body section.

It is preferred that the air flow valves disposed in the channels in the first and second sections of the mold body include at least one of four set positions, wherein in the first set position for generating a vacuum, both air flow valves are set to the air flow position and the air is in the position of the air flow. withdrawn from the mold body by both sections of the mold body, in the second position of the vacuum generating position, the first air flow valve is set to the air flow position, and the second air flow valve is set to the air block position, and air is drawn from the mold body only by the first mold body section, in the third position with cooling, the first air flow valve is set to the air block position, the second air flow valve is set to the air flow position, and air for cooling the mold body is introduced into the mold body through the second this section and is drawn out of the mold body through the first section, and in a fourth set position for blow molding, both air flow valves are set to the air flow position and air pressure is released from the mold body through both sections of the mold body. Each mold body section has a plurality of spaced apart slots in its inner surface, the slots in the first mold body section aligning with slots in the second mold body section, the first opening communicating with the slots in each mold body section. In addition, each section of the mold body has a mounting base, with an inlet to the air flow channel located at the mounting base. Each mold body section also has an airflow slot extending through its interior surface, the airflow channel including two divergent air paths through each mold body section, and each airway having an air manifold inlet provided at the mounting base of each mold body section and an opening. at the parting surface and the aperture of the gap between the collector opening and the aperture of the parting surface. The inner product forming surface of each mold body section is semicircular in shape and each air flow channel extends tangentially to the inner surface of each mold body section. Each mold body section includes a distal air passage between the first air passages, said distal air passage opening at one end into an air collector and at the other end into an air flow gap in the product-forming inner surface of each mold body section and a further air flow valve. which is also positioned between the air blocking position and the air flow position in the distal flow passage of the second mold body section.

The mold body of the present invention having the air flow valves described above has significantly increased versatility compared to the known Corma mold body.

The subject matter of the invention is illustrated in the drawing examples, in which Fig. 1 is a schematic view of a pipe forming apparatus, Fig. 2 is an enlarged perspective view of split sections of a mold body which meet with their parting surfaces to form a mold body according to a preferred embodiment. of the present invention, Figs. 3-6 are sectional views through a mold body formed by the mold body sections of Fig. 2 showing different positioning of the mold body, Fig. 7 is a perspective view of an air flow control area of one of the mold body sections of Fig. 2. also showing a specific type of air flow valve suitable for use in an air flow control area according to a preferred embodiment of the present invention, Fig. 7a is a view similar to Fig. 7 showing an alternative form of an air flow valve according to a further preferred embodiment of the present invention. of the invention, and Figs. 8 and 9 are sectional views through a simplified mold body showing different positions of operation of the air flow valve of Fig. 7.

Figure 1 shows a device for forming a pipe generally designated 1. The device comprises an extruder 2 that feeds a plastic melt into a mold intended to form a profiled tube generally designated P. This mold is formed by an upper set and a lower set of sections 3 and 5. a mold body, each section being moved around an endless path as shown in Fig. 1. Where the mold body sections meet each other, they form a moving mold tunnel.

Figure 2 shows in more detail the two mold body sections 3 and 5 which meet with their parting surfaces 4 and 6 to form the entire mold body.

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The mold body section 3 has a mounting base 7, which is a mold body region attached to a closed circuit track or to a mold body carriage (not shown) in an endless track. An air collector 9 is located in the mounting base of the mold body section 3. This manifold 9 is preferably permanently connected via the mold tunnel to an external source of compressed air which regulates or determines the air pressure inside the mold body. A similar manifold 29 is located in the chassis 27 of the mold body section 5.

The mold body section 3 includes an inner product-shaping surface, generally designated 15. The surface is formed by alternating ridges and grooves 17 and 19. A small gap 21 is provided around each of the semicircular recesses in the surface of the mold body section 3. in the groove, more than one slot 21 may be provided.

Mold body section 5 has an inner surface 35 shaped to the same shape as inner surface 15 and also having slots 38 as shown in Fig. 7. Slots in surface 35 mate with slots in inner surface 15 to form a series of juxtaposed continuous slits. around the formed circumferential grooves when the two sections of the mold body meet each other.

The mold body sections shown in Fig. 2 are used to form a ring-finned tube with the ribs on the tube spaced apart. Such mold body sections may be replaced by modified mold body sections used to form a helically finned tube, in which case, instead of separate cuts, one continuous helical notch will be made on the inner surface of the mold body.

The mold body section 3 further includes a plurality of air passages 11 passing through the mold body section. Similar air flow channels 30 are formed in the mold body section 5.

The inlets 8 of the air channels 11 open directly into the manifold 9. The air channels then run through the mold body section 3 divergent to opposite sides of the inner product-shaping surface 15. The channels extend tangentially to a semicircular product-shaping surface and terminate at openings 12 in the partitioning surface.

The air flow channels 30 in the mold body section 5 have openings 31 at the manifold 29 and openings 32 at the parting surface 6 of the mold body section 5.

When the two sections of the mold body come closer to each other, the openings 32 of the channels 30 at the index surface meet the openings 12 of the channels 11 at the index surface. As a result, a plurality of air passages are created extending completely through the mold body.

As shown in Fig. 2, there are a plurality of channels on each inner side, surface-shaping each section of the mold body. The channels are spaced apart along each section of the mold body.

Mold body section 3 includes a further set of shorter channels 13 extending from manifold 9 radially through mold body section 3. A similar set of short channels 33 extends from a manifold 29 in section 5 of the mold body.

The mold body section 3 includes a pair of openings 23 and a distal opening 25 through the mold body section 5. Each of these openings extends into indentations made in the interior surfaces of the two mold body sections. In section 3 of the mold body, the channels 11 open at the openings 23, and the channels 13 at the opening 25.

In the mold body section 5, the air channels 30 exit at the openings 37, and the channels 33 at the opening 39.

As can be seen from the above, in the mold body section 3, each of the channels 11 has openings at the manifold 9, at the opening 23 and at the parting surface of the mold body section 3. The channels 13 have their ends 14 at the manifold 9 and ends 16 at the opening 25. The openings 23 and 25 form air paths from the channels 11 and 13 to the cuts in the inner surface of the mold body section 3. A similar assembly is present in the mold body section 5, where the air passages 30 have openings at the manifold 29, at the openings 37 and at the parting surface of the mold body section 5. Moreover, the conduit 33 has a second end 36 at the opening 39 and an end 34 at the manifold 29.

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The openings 37 and 39 form direct air paths for the channels 30 and 33 to the cuts provided in the inner surface 35 of the mold body section 5.

The essence of the present invention is to provide air flow controls that regulate the movement of air in a mold body defined by the mold body sections 3 and 5. Figures 3-6 illustrate an embodiment of these airflow controls and illustrate positions they may assume to provide different mold body positions.

Figure 7 shows a lower mold body section 5 having a distal opening 48 which passes through spaced air passages 30. An opening 48 is formed between the opening 37 and the openings 32 of the channels 30 at the partitioning surface.

Although Fig. 7 shows only one side of the mold body section 5, the other side of this mold body section has an identical arrangement.

Rotary valve 49 fits into opening 48 extending through all air passages 30.

The valve 49 has a maximum diameter that is the same as the inner diameter of the opening 48. The valve has a series of flatness 55 along its length, each flat being located in one of the air passages 30. As shown in Fig. 8, the valve may have its flats parallel to the longitudinal axis of conduit 30 to allow air to flow through the valve, or it may be rotated 90 [deg.] From Fig. 8 to the position of Fig. 9, where the valve blocks air flow through the passages. .

Similar valves 45 are provided in the channels 11 and in the channels 13 of the mold body section 3. However, these valves are located between the upper ends of the channels 11 that open into the manifold 9 and the opening 23 through which the channels 11 pass. The operation of the valves 45 is identical to that of the valves 49. However, it should be noted that the valves 45 and 49 will operate independently of each other. each other.

Figure 7a shows an alternative type of valve 57 that is nothing more than a plug that is removed from the opening 48 of the mold body section 5 to allow air to move in both directions through the channels 30. However, when the plug is inserted into the opening 48, it blocks. air movement through the channels.

Each of the above types of valves can easily mate with sections of the mold body, the valve 49 has the advantage that it does not need to be removed, but can simply be turned by means of a valve head 51 into which a suitable tool is inserted.

The mold body described above is suitable for use in a wide variety of set-up positions. Some of these alignment positions are shown in Figures 3-6.

Particularly in Fig. 3 it can be seen that by keeping the two valves 45 and 49 open and by creating a vacuum in the manifolds 9 and 29 of the mold body sections 3 and 5, air is drawn along the cuts in the inner surfaces of the two mold body sections from the upper section 3. the mold body through the openings 23 and 25 and from the lower mold body section 5 through the openings 37 and 39. In this positioning position, a vacuum is generated in both sections of the mold body.

Figure 4 shows the situation where the valves 45 are closed and the valves 49 remain open. The manifold 29 of the lower mold body section 5 is subjected to a vacuum and air is drawn from the mold body, as indicated by the arrows in Fig. 4, from the lower mold body section only. However, it should be noted that due to the matching of the air channel openings in the parting surface in the upper and lower sections of the mold body some air is initially drawn out of the mold cavity not only through the openings in the lower section of the mold body but also from the openings 23 in the upper section of the mold body. . Although the vacuum is only acting from the lower section of the mold body, the upper section of the mold body is still subjected to the vacuum which ensures an even distribution of the plastic preform 61 that is used to form a tube with a completely circular internal cavity surface in the mold body.

The mold body of Fig. 4 has the advantage that it does not have to be used with a shaping device with a vacuum on both sides of the mold tunnel, but rather requires that vacuum systems be provided on one side of the mold tunnel, which substantially reduces the cost of the entire shaping device.

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In the construction of Fig. 5, it can be seen that, instead of using vacuum forming, blow molding, as indicated by arrows inside the blow molding 61, may be used to press the molding outwardly against the interior surfaces of the mold body sections. In such a case, as in the structure of Fig. 3, all the valves remain in the air flow position which allows the air trapped between the blow molding body and the inner surface of the mold body to be released to the outside through all air passages.

Figure 6 shows the mold body positioning position which is very unique and advantageous. This set position is used to cool both the pipe inside the moving mold tunnel and the mold body sections as they move along the mold tunnel.

More specifically, after initially shaping the tube in the mold tunnel, using any of the shaping methods of Figs. 3-5, there will be a tendency for the tube to contract from the inner wall surfaces of the mold body section. This occurs while the tube is still in the mold tunnel. As a result, a gap G is formed between the shaped tube and the inner wall surface of the mold body. The construction of Fig. 6 takes advantage of this tube shrinkage to provide better cooling of both the tube and the mold body sections.

More specifically, the valves 49 in the lower section 5 of the mold body are set in an air-blocking position, while all the valves in the upper section of the mold body are in an air flow position. Air, which may be ambient air or cooled air, is taken from outside of the lower mold body section 5 and is introduced from the base of the lower mold body section and along channels 30 and 33 into slot G through openings 37 and 39. This air then flows around the tube. at the slot G and is pulled through the openings 23 and 25 from the mold body section 3, with the manifold 9 of this section under a negative pressure. The valves 49, which are in the blocked position, prevent cooling air from being drawn directly through the mold body without flowing around the pipe.

The cooling air not only has a cooling effect on the pipe, but additionally has a cooling effect on each of the mold body sections initially as it flows through the mold body section 5 and then as it is drawn through the mold body section 3.

While the description details various preferred embodiments of the present invention, it should be emphasized that those skilled in the art may also devise certain variants of the invention falling within the scope of protection as defined in the claims.

Claims (7)

A mold body with airflow / adaptation control in a moving mold tunnel comprising first and second sections each having an interior article-forming surface and a parting surface, characterized in that each mold body section (3, 5) further comprises a first channel (11,30) of the air flow, each channel having an inlet (8,31) and a first opening (23,37) in each channel for an inner product-forming surface (15,35) and a second opening (12,32) to a surface. the division (4, 6), the second opening (12) of the channel (11) in the first section (3) of the mold body being connected to the second opening (32) of the channel (30) in the second section (5) of the mold body when the body sections the molds are closed at their partition surfaces, and have first and second air flow valves (45, 49), each of the valves (45, 49) being controlled independently of one another between an air flow position and an air block position, and a first valve (45) flow the air port is positioned between the first opening (23) and the inlet (8) in the duct (11) of the first mold body section (3), and the second air flow valve (49) is positioned between the second opening (32) and the first opening (37) in the channel (30) of the second mold body section (5). 2. A mold body according to claim 1. The mold body of Claim 1, characterized in that the air flow valves (45, 49) disposed in the channels (11, 3u) in the first and second sections (3, 5) of the mold body include at least one of four set positions, wherein the first set position is up to to create a vacuum, both air flow valves (45, 49) are set to the air flow position, and air is drawn from the mold body through both sections (3, 5) of the mold body, in a second position to create a vacuum, the first valve (45) The airflow is set to the airflow position and the second airflow valve (49) is set to the air blocked position, and air is drawn from the mold body through the first mold body section (3) only, in the third set position with cooling, the first valve (45) the air flow is set to the air block position, the other air flow valve (49) is set to the air flow position, and the air is set to cool. The mold body is inserted into the mold body through the second section (5) and is drawn out of the mold body through the first section (3), and in a fourth set position for blow molding, both air flow valves (45, 49) are set at position of the air flow and air pressure is released from the mold body through both sections (3, 5) of the mold body. 3. A mold body according to claim 1. The mold body of Claim 1, characterized in that each mold body section (3, 5) has a plurality of spaced apart slots (21, 38) in its inner surface (15, 35), the slots (21) in the first section (3) The mold body is aligned with slots (38) in the second section (5) of the mold body, the first opening (23, 37) being connected to the slots (21, 38) in each section (3, 5) of the mold body. 4. A mold body according to claim 1. The mold body according to claim 1, characterized in that each section (3, 5) of the mold body has a mounting base (7, 27), the inlet (8, 31) to the air flow channel (11, 30) being located at the mounting base (7, 27). 27). 5. A mold body according to claim 1. The mold body according to claim 4, characterized in that each mold body section (3, 5) has an air flow slot (21, 38) extending through its inner surface (15, 35), the air flow channel (11, 30) having two diverging air paths. through each mold body section, and each air path has an air inlet (8, 31) at the air manifold (9, 29) provided at the mounting base (7, 27) of each mold body section (3, 5) and an opening (12, 32) at the partitioning surface and the opening (23, 37) of the gap between the collector opening and the partitioning surface opening. 6. A mold body according to claim 1. The mold body of claim 5, characterized in that the inner product forming surface (15, 35) of each mold body section (3, 5) has a semicircular shape and each 189 132 an air flow channel (11, 30) extends tangentially to the inner surface in each section of the mold body. The mold body according to claim 1. a, /. characterized in that each portion (k, 5) of the body and company comprises a further air passage (13, 33) between the first air channels (11, 30), said further air passage (13, 33) exiting at one end (14, 34) into an air collector (9, 29), and at the other end (16, 36) into an air flow slot (21, 38) in the article-forming inner surface (15, 35) of each mold body section; and a distal air flow valve (47) which is also positioned between an air block position and an air flow position in the distal flow passage (13) of the second mold body section (3).